The majority of modem portable communication and computing devices (such as mobile phones, smartphones, tablet computers, etc.) are supplied from a battery pack with one or more battery cells connected in parallel. In many cases these battery cells are Li-Ion based cells, which deliver the effective battery capacity at a typical output voltage of approx. 3.7V (e.g. in the range of 3.2-4.2V). The processor IC (integrated circuit) of such computing devices is typically an important power sink, especially when the computing device is executing high performance computing tasks such as internet browsing, high resolution video and/or gaming. The central processing units (CPU) and graphic processing units (GPU) of the processor IC, as well as the required memory (DDR) are typically biased at voltages in the range of less than 1.8V. The rails for these biased voltages are typically generated using regulators inside a power management unit (PMU). In view of the high current demand of modem application processors (up to multiple Amperes per rail) these regulators are typically implemented as inductor-based switching buck converters. An inductor-based switching buck converter may convert power from the input voltage to the output voltage by regulating the duty cycle of a power switch comprised within the converter. By doing this, power may be converted in a more efficient way than by using linear regulators that dissipate power proportional to the voltage drop from input voltage to output voltage.
Another important power sink of modem electronic devices is the LCD backlight of a panel or display. The power required by the LCD backlight typically increases with the growing size and resolution of the panel. The backlight is typically implemented via one or multiple strings of serial LEDs, which are supplied with 12-60V supply voltage. This high voltage rail is typically generated via a switching inductor-based boost converter. Especially for large displays, the backlight dissipation power can be in a similar range or even higher than the average power needed for the application processor and memory.
Battery supplied electronic devices have a limited mobility time defined by the battery pack capacity, the average power consumption and the efficiency of the regulators used within the electronic devices. The maximum battery capacity is typically limited by the dimensions of the electronic device. The limited battery capacity leads to restrictions for the selection of the LCD panel size/resolution and the required maximum and average device computing performance. Furthermore, the total dissipation power of the power sinks may reach the thermal budget of fan-less computing devices like smartphones and tablet computers. Other portable computers (like notebooks and netbooks) may be forced to implement dedicated cooling systems to prohibit a device overheating at high computational load and/or at high display brightness.
In view of the above, there is a need for power efficient regulators, which may be used to derive electrical power at different voltages from the electrical power provided by a battery pack.